Coating processes – Immersion or partial immersion
Reexamination Certificate
2001-01-04
2004-06-08
Lamb, Brenda A (Department: 1734)
Coating processes
Immersion or partial immersion
C427S402000, C118S423000, C118S066000, C204S198000, C204S202000
Reexamination Certificate
active
06746720
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a conveyance apparatus which causes a workpiece which is supported by a conveyor to pass through a plurality of treating processes while changing the workpiece position, and more particularly to a conveyance apparatus which is suitable for a surface treatment line such as a car body painting line in a vehicle manufacturing factory.
Also, the present invention relates to a conveyance apparatus which is preferably used in a line in which different kinds of workpieces, made of materials such as resin, metal or the like, requiring different treating conditions, are mixed.
Further, the present invention relates to a conveyance apparatus for multi-color painting. In the present invention, a floor conveyor position is defined as a workpiece position in which a workpiece is secured to a platform and is supported by resting on the conveyor, and an overhead conveyor position is defined as a workpiece position in which a workpiece is supported by hanging. In addition, a side conveyor position is a workpiece position in which a workpiece is supported approximately horizontally to a side direction of a conveyor. Also, horizontal rotation means rotation in a plane vertically intersecting the direction of travel.
2. Description of the Prior Art
In a painting line for a vehicle, there are many treating processes such as pretreatment, electrodeposition, washing, painting, and drying. A workpiece is transferred among these treating processes by a conveyor. When painting a comparatively large body of, for example, a four-wheel vehicle by dipping is required, as shown in
FIG. 11A
, a workpiece W which has been transferred along a floor conveyor FC located on a floor is then transferred to and suspended from an overhead conveyor HC which is arranged to move vertically relative to a painting line. In such a condition, the workpiece W is caused to pass above pretreatment and electrodeposition baths and the like, while the conveyor itself is arranged to move vertically relative to the pretreatment and electrodeposition baths and the like. In this manner, the workpiece W is moved vertically to undergo dipping treatment and then transferred again to the floor conveyor FC.
Also, in the case of electrodeposition, to obtain fine painting quality, it is known that the workpiece must be rotated in an electrodeposition paint bath to change its position to a successive variety of positions (e.g. see Japanese Patent Publication No. Hei 6-104920 and Japanese Unexamined Patent Publication No. Hei 2-111481). Japanese Patent Publication No. Hei 6-104920 also discloses that the body undergoes electrodeposition by dipping. This method is a so-called batch type processing, in which an elevator mechanism for moving the body vertically relative to a dipping treatment bath, and a rotational mechanism for rotating the body immerged in a solution are provided. Dipping is performed by a double action of an upward and downward movement and subsequent rotation.
On the other hand, when painting a comparatively small body of a two-wheel vehicle is required, as shown in
FIG. 11B
, all the painting processes can be performed using the overhead conveyor HC. Accordingly, it is no longer necessary to transfer the body to other positions while being painted as with the four-wheeled vehicle, but the dipping treatment still requires the vertical operation in the same manner as shown above.
In a process wherein the workpiece position must be changed to the floor conveyor position and the overhead conveyor position, if the workpiece must be transferred whenever the workpiece position is changed while being conveyed, loss of time is caused. It is therefore desired to avoid transfer of the workpiece while it is being conveyed at least in one continuous process even though the workpiece position changes. Further, in a method such as a dipping treatment of the prior art wherein a conveyance line is continuously changed vertically, the proportion of time unusable for dipping but required only for immersing the workpiece in and removing it from a bath becomes large relative to the substantial dipping time of the workpiece. Accordingly, it is desired to reduce this loss of time. Also, in the case of the overhead conveyor, there is some possibility that the painting quality deteriorates if dust and the like falling from the overhead conveyor adhere to the workpiece. It is therefore desired to realize a conveyance method that makes it difficult for such falling substances to adhere to the workpiece. It is therefore a first object of the present invention to solve the above-mentioned disadvantages.
In a painting line in which processes are carried out in the order of a pretreatment process, painting process and drying process, the treating conditions in the pretreatment process and the drying process differ according to whether the workpiece is made of resin or of metal. For this reason, the treatments have been performed by providing an exclusive line for resin workpieces and another for metal workpieces, or switching one line depending on the material handled.
In the case of providing an exclusive line relative to the above mentioned different kinds of materials, since the amount of equipment required doubles the installation space and investment could increase. In the case of switching the line depending on the material, a loss occurs because a lot of time for switching is spent for washing the apparatus (pretreatment process), control of temperature (drying process) or the like after switching. Moreover, this loss may become larger, and in order to reduce it, it is necessary to produce the workpieces in lots. However, if produced in lots, it is impossible to produce in synchronization with another department. It is a second object of the present invention to solve such disadvantages.
In electrodeposition painting of a body of vehicle, a conveyor is generally disposed above a painting bath, and a workpiece hung from and moved by the conveyor is lowered into the painting bath and is dip-treated therein (for example, see Japanese Patent Publication No. Hei 6-104920). Also, in the case where a plurality of different colors are painted by using such a painting line, methods shown in A and B of
FIG. 2
are utilized.
In the method A, separate painting baths T
1
, T
2
for two different colors (color
1
and color
2
) are arranged side by side, and diverging conveyor lines B
1
, B
2
are arranged above the painting bath, each of the diverging lines B
1
, B
2
being connected with a main line M before and after the painting baths. A workpiece is diverted to either of the diverging lines B
1
or B
2
according to the required color (either the color
1
or the color
2
) and is dipped into the corresponding painting bath T
1
or T
2
. Hereinafter, this is referred to as a diverging method. The method B is so designed that the main line M of the conveyor is arranged above a single painting bath T
3
, and the painting bath T
3
and T
4
are exchanged whenever the color is to be changed to either the color
1
or the color
2
. Hereinafter, this is referred to as a color replacement method.
In the above-mentioned diverging method, because the main line M is separated into the diverging lines B
1
, B
2
, the total length of the conveyance line is increased. This causes an increase in both equipment costs and installation space. In the color replacement method, much time is required to replace the painting baths and the efficiency is reduced. Accordingly, to solve such disadvantages, it is a third object of the present invention to provide a conveyance apparatus for performing selectively painting of two different colors without increasing the length of the line and replacing the painting bath.
SUMMARY OF THE INVENTION
To solve the above-noted disadvantages, a first invention provides a dipping treatment apparatus having a conveyor disposed above a treatment bath for dipping and the like and designed to cause a workpiece which is conveyed by the conveyor to be immers
Nishida Hidenobu
Sakai Makoto
Honda Giken Kogyo Kabushiki Kaisha
Lamb Brenda A
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